The present invention pertains to an apparatus for generating a tactile force for a vehicle, and in particular to an apparatus which generates not only a tactile force for depression and restoration of an accelerator pedal but also a tactile force and a detent force for a shift lever, introducing a combination of a spring, a motor and an electromagnetic brake.
When a driver of a vehicle manipulates its shift lever or pedal, with which he gives directions to it, he feels a reaction force in his hand or foot, which is generated according to an amount of manipulation of the lever or the pedal. In this connection, a haptic device is known, in which the shift lever and the accelerator pedal are used not only as input apparatus but also as output apparatus.
The applicant of the present invention filed Japanese Patent Application 2002-101860 (Japanese Published Patent Application 2003-291682) titled “VEHICULAR ACCELERATOR PEDAL DEVICE”. FIG. 10 of this application is a block diagram showing a conventional vehicular accelerator pedal device and FIG. 11 is a graph depicting operational characteristics of the device. As shown in FIG. 11, from the bottom to top of a vertical axis are shown a signal FS2 of pedal depression, a throttle angle θTH2, transmission information TJ2, a tactile force RT2 exerted by a tension coil spring, a tactile force RM2 exerted by a motor and a pedal tactile force RP2 which is a summation of RT2 and RM2. On the other hand, a horizontal axis represents an amount PS2 of pedal depression.
As shown in FIGS. 10 and 11, when a driver depresses an accelerator pedal 150, the signal FS2 starts increasing when once the amount PS2 reaches S10. The throttle angle θTH2 starts increasing, accordingly.
The tactile force RT2 steeply increases until the amount PS2 reaches S10. After the amount PS2 reaches S10, the tactile force RT2 starts increasing in proportion to the amount PS2. Thereafter, when the amount PS2 reaches S30, the tactile force RT2 reaches F13.
The tactile force RM2 exerted by a motor 260b is not generated until the amount PS2 reaches S20. When the amount PS2 reaches S20, the tactile force RM2 starts steeply increasing, and when the amount PS2 subsequently reaches S30, the transmission information TJ2 rises from a LOW level to a HIGH level so as to change the transmission of a vehicle. At this point, the transmission starts a kick-down, and the tactile force RM2 exerted by the motor 260b which has been increasing starts steeply decreasing, accordingly. In this connection, the tactile force RM2 takes a local maximum F12 when the amount PS2 reaches S30. When the amount PS2 reaches S40, the motor 260b comes to a stop, making the tactile force RM2 zero. Accordingly, the transmission information TJ2 changes from the HIGH level to the LOW level.
A summation of the tactile forces RT2 and RM2 exerted respectively by the spring and the motor 260b makes the pedal tactile force RP2. For example, F13 of the tactile force RT2 and F12 of the tactile force RM2 at S30 of the amount PS2 result in a local maximum F11 of the pedal tactile force RP2.
It may be possible to save the power consumed by the vehicle by introducing the pedal tactile force RP2 generated by a combination of the tension coil spring 720 and the motor 260b, because it is only necessary for the motor 260b to operate while the amount PS2 of pedal depression falls in a rang of S20 to S40. Furthermore, compared with a system which generates the pedal tactile force only by the motor 260b, it may be possible to adopt a motor with a smaller output power and reduce the cost associated with the motor.
In this way, it is feasible to select a more compact motor because it is possible to decrease the power required of the motor by use of the tension coil spring 720.
However, it is necessary to provide a hysteresis of the accelerator pedal between its depression and restoration so that the operability of the vehicle can be improved. The reason why the hysteresis is necessary can be understood if a system without hysteresis is assumed as an example. When the system does not have the hysteresis, it makes the control of the pedal difficult in such cases as constant-speed cruising and vibration of the vehicle on an uneven road, because the pedal tends to move too sensitively in response to a negligible change in force imposed on the pedal. In order to overcome a drawback described above, the motor 260b is kept being in operation during the pedal restoration.
The applicant of the present invention also filed Japanese Patent Application 2002-66374 (Japanese Published Patent Application 2003-260948) “VEHICLE TRANSMISSION”, which discloses related arts. In this document, a vehicle transmission is disclosed, which can change a shift pattern and a shift lever position with an electric force, so that the operability of a vehicle is improved. FIG. 12 is a block diagram showing a conventional transmission apparatus A. FIGS. 13A and 13B are schematic diagrams illustrating transmission patterns (shift patterns): FIG. 13A for an automatic transmission pattern and FIG. 13B for a manual transmission pattern, respectively. As shown in FIGS. 12, 13A and 13B, the transmission apparatus A includes a shift lever 910, a direction sensor 930, an engine control unit (ECU) 940, a mode selection switch 970, an actuator 990 for forward-backward tactile force and a monitor 200. If the monitor 200 shows the automatic transmission pattern as shown in FIG. 13A, a predetermined detent force is exerted on the shift lever 910 according to the selected positions P, R, N—. This force is given in such a manner that it is exerted as a small tactile force in a direction of sliding of the shift lever before its manipulation and subsequently as another tactile force to guide it to the next shift position.
Next in the manual transmission pattern as shown in FIG. 13B, when the shift lever 910 is moved forward or backward with regard to a neutral position (base position) M, a predetermined tactile force is determined by an operational tactile force control module (not shown) and the signal indicative of the tactile force is delivered to the actuator 990 (see FIG. 12). When the shift lever 910 is released, the ECU 940 delivers a signal to the actuator 990, which is indicative of slow restoration of the shift lever 910 to the neutral position M.
Another apparatus for generating a tactile force for a vehicle is also disclosed. This apparatus provides each one of a plurality of objects, which is selected by a driver to manipulate, with a tactile force correlated with it. In other words, the tactile force varies from one object to another. When the driver manipulates the object while the tactile force is exerted on it, the driver experiences a tactile impression associated with such as manipulating a shift lever, depressing a pedal or touching an air conditioner switch. In parallel to this, the selected object is controlled according to a position of the object as a result of manipulation by the driver.
As shown in FIG. 14, for example, an apparatus 900 for generating a tactile force for a vehicle has an engine control unit (ECU) 700. The apparatus 900 further includes a pedal device 720 having a pedal 720a on which a foot of the driver rests and an arm 720b. The arm 720b is coupled to a stroke simulator 760 via a shaft 740. When the pedal 720 is depressed, the shaft 740 moves into the stroke simulator 760, which generates a tactile force according to an amount of working oil coming into the stroke simulator 760. In this way, the tactile force according to a stroke of the pedal 720 is exerted on the pedal assembly 720. A stroke sensor 780, which delivers an electric signal according to the stroke of the pedal 720 to the ECU 700, is attached to the shaft 740. The ECU 700 detects the stroke of the pedal assembly 720 according to the output signal of the stroke sensor 780. A throttle unit 840 provides a brake unit 860 with a command signal so that a throttle angle or a brake force according to the stroke of the pedal assembly 720 can be implemented. For example, Japanese Published Patent Application 2001-105926 reports the related arts.
However, it was necessary to keep a motor in operation during the restoration of a pedal so as to provide a hysteresis relative to the depression aiming at the better operability of a vehicle. Furthermore, it was demanded that the motor be activated much less frequently so as to save power.
The motor, which generates a tactile force for an accelerator pedal during its depression and restoration, provides the driver of a vehicle with a tactile impression for its maneuver via the accelerator pedal. It was necessary to elaborate on the compactness of the motor for power saving.
It was also necessary to activate a motor less frequently, which is used for generating a detent force for a shift lever, so as to achieve power saving.